1. Field of the Invention
The present invention relates to a new type of segmented fin for use on a finned tube, specialized serrating wheels for creating the new type of segmented fin, and the process for employing the specialized serrating wheels to create the new type of segmented fin.
The new type of segmented fin is unique because it is provided with individual segments that are curved in order to increase the heat transfer rate of the finned tube that is created when the fin is welded onto a heat exchanger tube. In addition, the segments are coined by the specialized serrating wheels, thus increasing the surface area of the segments and further shaping the sheared edges of each of the segments to result in segments with less air drag.
2. Description of the Related Art
Adding fins to the external surface of a heat exchange tube is an old and well-known way to increase the heat transfer rate between the exterior of the tube and the interior of the tube. Increased heat transfer rate is desirable because the purpose of the heat exchange tubes is to transfer heat between a liquid or gas located within the tube and a liquid or gas located outside the tube. Fins are normally attached to the external surface of the finned tube by employing a long, continuous fin that is wound in helical fashion around the tube so that the fin extends approximately perpendicular to the tube's longitudinal axis.
The practice of serrating the outward extending side of the fin to create segments in the fin prior to winding the flat, non-serrated inwardly extending side or base of the fin to the tube is also a commonly employed way of further increasing the heat transfer rate of the finned tube.
In addition, a variety of surface enhancements to the serrated portion of the fin have been proposed as means for further increasing the surface area of the segments and thus increase the heat transfer rate of the finned tube. One of the disadvantages of creating most of these types of surface enhancements in the segments is that the enhancements increase drag on the outside of the finned tube, either by the gas or liquid flowing past the fins external to the tube.
The present invention further increases the heat transfer rate of serrated finned tubes by creating a serrated fin that has curved segments. Each of these curved segments is concave on one side of the segment and is convex on the opposite side of the segment. This curvature of the segments results in better attachment of the external gas or liquid to the surfaces of the segments, resulting in a higher heat transfer rate. The curvature of the segments also makes them stronger. In addition, the segments are coined or pressed between the serrating wheels to further increase the surface area of the segments and to shape the edges of the segments. Increasing the surface area of the segments allows them to be more efficient at transferring heat and shaping the edges of the segments allows them to be more aerodynamic so that there is decreased drag on the fin when the finned tube is in service.
Finally, after serrating and coining the segments, the segments are passed between a final set of wheels in order to precisely align the segments relative to their base, making the fin ready for winding onto the tube to create a finned tube.